Cellular radio networks are constantly evolving. One feature introduced in Wideband Code Division Multiple Access (WCDMA) networks is High Speed Packet Access (HSPA) that is used to enhance data rates within the radio network. During High Speed (HS) serving cell change from one Node B (alternatively referred to as a Radio Base Station, RBS) to another Node B, the central control node also referred to as Radio Network controller (RNC) decides a time for the old Node B to stop sending data and for the new node B to start to send data. During so-called Multi Point Transmission (MP Transmission) High Speed Downlink Packet Access (HSDPA) operation, which is currently agreed in 3GPP to support in Release 11 (Rel-11), the RNC should split the data and send the data via two, or more, cells in one Node B (Intra Node B MP Transmission), or two cells in different Node Bs (Inter Node B MP Transmission).
There is a constant demand for improving existing systems and to provide more efficient transmission in a cellular radio system. Hence, there is a need for a method and an apparatus that provide an improved transmission in a cellular radio system.